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Abstract:

A digital broadcast system and a data processing method are disclosed. A
data processing method of a digital broadcast transmission system
includes delaying a reference time of a program clock reference (PCR)
based on a size of mobile service data, when processing a broadcasting
signal including main service data and the mobile service data, verifying
a transport stream system target decoder (T-STD) model based on the PCR
of the delayed reference time, and storing a packet of the main service
data in an auxiliary buffer, when overflow of a buffer in the T-STD model
is estimated as the verification result of the T-STD model.

Claims:

1-15. (canceled)

16. A data processing method of a transmitter, the method comprising:
adjusting packet timing and a program clock reference (PCR) of main
service data packets; encoding mobile service data for forward error
correction (FEC); encoding signaling data for signaling the mobile
service data; forming data groups, wherein at least one of the data
groups includes the encoded mobile service data, the encoded signaling
data, a moving picture experts group (MPEG) header place holder, and a
main service place holder; removing the main service place holder and
replacing the MPEG header place holder with an MPEG header to form mobile
service data packets; multiplexing the mobile service data packets and
the main service data packets; and transmitting a transmission frame
including the multiplexed data packets

17. The method of claim 16, further comprising: systematic RS encoding
main service data in the multiplexed data packets; and non-systematic RS
encoding mobile service data in the multiplexed data packets.

18. The method of claim 16, wherein the at least one of the data groups
further includes a plurality of known data sequences.

19. A transmitter for data processing, the transmitter comprising: an
adjustment unit configured to adjust packet timing and a program clock
reference (PCR) of main service data packets; an encoder configured to
encode mobile service data for forward error correction (FEC); a
signaling encoder configured to encode signaling data for signaling the
mobile service data; a group formatter configured to form data groups,
wherein at least one of the data groups includes the encoded mobile
service data, the encoded signaling data, a moving picture experts group
(MPEG) header place holder, and a main service place holder; a packet
formatter configured to remove the main service place holder and replace
the MPEG header place holder with an MPEG header to form mobile service
data packets; a multiplexer configured to multiplex the mobile service
data packets and the main service data packets; and a transmission unit
configured to transmit a transmission frame including the multiplexed
data packets

20. The transmitter of claim 19, further comprising: a
systematic/non-systematic RS encoder configured to systematic RS encode
main service data in the multiplexed data packets and non-systematic RS
encode mobile service data in the multiplexed data packets.

21. The apparatus of claim 19, wherein the at least one of the data
groups further includes a plurality of known data sequences.

22. A data processing method of a receiver, the method comprising:
receiving a broadcast signal including main service data packets and
mobile service data packets, wherein the broadcast signal is processed in
a transmitter by: adjusting packet timing and a program clock reference
(PCR) of main service data packets; encoding mobile service data for
forward error correction (FEC); encoding signaling data for signaling the
mobile service data; forming data groups, wherein at least one of the
data groups includes the encoded mobile service data, the encoded
signaling data, a moving picture experts group (MPEG) header place
holder, and a main service place holder; removing the main service place
holder and replacing the MPEG header place holder with an MPEG header to
form mobile service data packets; and multiplexing the mobile service
data packets and the main service data packets; de-multiplexing the
broadcast signal; decoding the signaling data in the de-multiplexed
broadcast signal; and decoding the de-multiplexed broadcast signal.

23. The method of claim 22, wherein the broadcast signal is further
processed in the transmitter by: systematic RS encoding main service data
in the multiplexed data packets; and non-systematic RS encoding mobile
service data in the multiplexed data packets.

24. The method of claim 22, wherein the at least one of the data groups
further includes a plurality of known data sequences.

25. A data receiver for processing, the receiver comprising: a receiving
unit configured to receive a broadcast signal including main service data
packets and mobile service data packets, wherein the broadcast signal is
processed in a transmitter by: adjusting packet timing and a program
clock reference (PCR) of main service data packets; encoding mobile
service data for forward error correction (FEC); encoding signaling data
for signaling the mobile service data; forming data groups, wherein at
least one of the data groups includes the encoded mobile service data,
the encoded signaling data, a moving picture experts group (MPEG) header
place holder, and a main service place holder; removing the main service
place holder and replacing the MPEG header place holder with an MPEG
header to form mobile service data packets; and multiplexing the mobile
service data packets and the main service data packets; a de-multiplexer
configured to de-multiplex the broadcast signal; a signaling decoder
configured to decode the signaling data in the de-multiplexed broadcast
signal; and a decoder configured to decode the de-multiplexed broadcast
signal.

26. The receiver of claim 25, the broadcast signal is further processed
in the transmitter by: systematic RS encoding main service data in the
multiplexed data packets; and non-systematic RS encoding mobile service
data in the multiplexed data packets.

27. The receiver of claim 25, wherein the at least one of the data groups
further includes a plurality of known data sequences.

Description:

[0001] This application claims the benefit of 61/029,550, filed on Feb.
18, 2008, which is hereby incorporated by reference as if fully set forth
herein. Also, this application claims the benefit of Korean Application
No. 10-2009-0012635, filed on Feb. 16, 2009, which is hereby incorporated
by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a digital broadcast system, and
more particularly, to a digital broadcast transmission system, a digital
broadcast receiver, and a data processing method of the digital broadcast
transmission system and the digital broadcast receiver.

[0004] 2. Discussion of the Related Art

[0005] A digital broadcast system may include a digital broadcast
transmitter and a digital broadcast receiver. The digital broadcast
transmitter digitally processes data of a broadcasting program etc. and
transmits the processed data to the digital broadcast receiver. Such a
digital broadcast system is replacing an analog broadcast system, due to
various advantages such as the efficiency of data transmission.

[0006] Recently, research into the digital broadcast receiver, which is
capable of receiving broadcasting signals while moving, has been
conducted. A digital broadcast transmission system can transmit both
broadcasting signals for a fixed digital broadcast receiving system and
broadcasting signals for a mobile digital broadcast receiving system.

[0007] However, according to the prior art, if the broadcasting signals
for the mobile digital broadcast receiving system are simply added to the
broadcasting signals for the fixed digital broadcast receiving system, an
unexpected overflow or underflow problem in a buffer occurs frequently.

SUMMARY OF THE INVENTION

[0008] Accordingly, the present invention is directed to a digital
broadcast system and a data processing method that substantially obviate
one or more problems due to limitations and disadvantages of the related
art.

[0009] An object of the present invention is to provide a digital
broadcast system and a data processing method which do not generate an
overflow or underflow problem even when both broadcasting signals for a
fixed digital broadcast receiving system and broadcasting signals for a
mobile digital broadcast receiving system are processed.

[0010] Additional advantages, objects, and features of the invention will
be set forth in part in the description which follows and in part will
become apparent to those having ordinary skill in the art upon
examination of the following or may be learned from practice of the
invention. The objectives and other advantages of the invention may be
realized and attained by the structure particularly pointed out in the
written description and claims hereof as well as the appended drawings.

[0011] To achieve these objects and other advantages and in accordance
with the purpose of the invention, as embodied and broadly described
herein, a data processing method of a digital broadcast transmission
system includes delaying a reference time of a program clock reference
(PCR) based on a size of mobile service data, when processing a
broadcasting signal including main service data and the mobile service
data, verifying a transport stream system target decoder (T-STD) model
based on the PCR of the delayed reference time, and storing a packet of
the main service data in an auxiliary buffer, when overflow of a buffer
in the T-STD model is estimated as the verification result of the T-STD
model.

[0012] In another aspect of the present invention, a data processing
method of a digital broadcast receiver includes receiving a broadcasting
signal including a main service data packet, a mobile service data
packet, and a program clock reference (PCR), reference time of which is
delayed, wherein the broadcasting signal includes a null data packet
instead of the main service data packet, according to a result of a
verification process of the T-STD model of a digital broadcast
transmission system, demultiplexing the received broadcasting signal, and
decoding the main service data packet, which is demultiplexed, according
to the PCR.

[0013] In a further aspect of the present invention, a digital broadcast
transmission system includes a delay for delaying a reference time of a
program clock reference (PCR) based on a size of mobile service data,
when processing a broadcasting signal including main service data and the
mobile service data, a verifier for verifying a transport stream system
target decoder (T-STD) model based on the PCR of the delayed reference
time, and an auxiliary buffer for storing a packet of the main service
data according to a verification result of the T-STD model.

[0014] In another aspect of the present invention, a digital broadcast
receiver includes a receiver for receiving a broadcasting signal
including a main service data packet, a mobile service data packet, and a
program clock reference (PCR), reference time of which is delayed,
wherein the broadcasting signal includes a null data packet instead of
the main service data packet, according to a result of a verification
process of the T-STD model of a digital broadcast transmission system, a
demultiplexer for demultiplexing the received broadcasting signal, and a
decoder for decoding the main service data packet, which is
demultiplexed, according to the PCR.

[0015] It is to be understood that both the foregoing general description
and the following detailed description of the present invention are
exemplary and explanatory and are intended to provide further explanation
of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a
part of this application, illustrate embodiment(s) of the invention and
together with the description serve to explain the principle of the
invention. In the drawings:

[0017] FIG. 1 is a block diagram illustrating the construction of a T-STD
which is one type of digital broadcast transmission system;

[0018]FIG. 2 is a block diagram illustrating the construction of a
digital broadcast transmission system according to an exemplary
embodiment of the present invention;

[0019] FIG. 3 is a diagram illustrating fullness of data stored in a
transport buffer of the T-STD of FIG. 1, when only main service data is
processed without mobile service data;

[0020]FIG. 4 is a diagram illustrating fullness of data stored in a
transport buffer of the T-STD of FIG. 1, when both mobile service data
and main service data are processed;

[0021] FIG. 5 is a diagram illustrating fullness of data stored in a main
buffer of the T-STD of FIG. 1 before PCR adjustment, when both mobile
service data and main service data are processed;

[0022]FIG. 6 is a diagram illustrating fullness of data stored in a
transport buffer of the T-STD of FIG. 1 after PCR adjustment, when both
mobile service data and main service data is processed;

[0023] FIG. 7 is a flow chart illustrating a data processing method of a
digital broadcast transmission system according to an exemplary
embodiment of the present invention; and

[0024] FIG. 8 is a block diagram illustrating a digital broadcast receiver
according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Reference will now be made in detail to the exemplary embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings. The exemplary embodiments of the invention may be
modified in various forms and the invention should not be limited to the
specific embodiments described herein.

[0026] Although the terms used in the present invention are selected from
generally known and used terms while considering functions of the present
invention, they may vary according to intention or customs of those
skilled in the art or to emergence of new technology. Some of the terms
mentioned in the description of the present invention may have been
selected by the applicant at his or her discretion, and in such cases the
detailed meanings thereof will be described in relevant parts of the
description herein. Thus, the terms used in this specification should be
interpreted based on the substantial meanings of the terms and the whole
content of this specification rather than their simple names or meanings.

[0027] Among the terms used in the description of the present invention,
main service data corresponds to data that can be received by a fixed
receiving system and may include audio/video (A/V) data. More
specifically, the main service data may include high definition (HD) or
standard definition (SD) A/V data and may also include diverse data types
required for data broadcasting. Moreover, known data refers to data that
is pre-known by an agreement between a receiving side and a transmitting
side

[0028] Among the terms used in the description of the present invention,
MH indicates respective first letters of the words "mobile" and
"handheld" and is an opposite concept to a fixed type. MH service data
may include at least one of mobile service data and handheld service
data, and will be referred to as mobile service data for convenience of
description. Herein, the mobile service data may include not only the MH
service data but also any type of service data indicating mobile or
portable characteristics. Therefore, the mobile service data according to
the present invention is not limited only to the MH service data.

[0029] The above-described mobile service data may correspond to data
having information, such as program execution files, stock information,
etc., and may also correspond to A/V data. Particularly, the mobile
service data may correspond to A/V data having lower resolution and lower
data rate as compared to the main service data, as the service data for
portable or mobile terminals (or a broadcast receiver). For example, if
an A/V codec that is used for a conventional main service is an MPEG-2
codec, an MPEG-4 advanced video coding (AVC) or scalable video coding
(SVC) having better image compression efficiency may be used as the A/V
codec for the mobile service. Furthermore, any type of data may be
transmitted as the mobile service data. For example, transport protocol
expert group (TPEG) data for broadcasting real-time transportation
information may be transmitted as the mobile service data.

[0031] A transmitting system of the present invention provides backward
compatibility in the main service data so as to be received by a
conventional receiving system. The main service data and the mobile
service data can be multiplexed on the same physical channel and then be
transmitted.

[0032] FIG. 1 is a block diagram illustrating the construction of a
transport stream system target decoder (I-STD) which is one type of
digital broadcast transmission system. The T-STD may correspond to a
moving picture experts group 2 (MPEG2) T-STD. The T-STD performs models
of a digital broadcast receiver and adjusts an encoder of the digital
broadcast receiver using the modeling result. In FIG. 1, t(i) denotes an
input time of an i-th byte of a transport stream (TS), and a bit rate
received at that time is about 19.39 Mbps for example.

[0033] Traveling paths of input TS packets are determined according to
packet identifiers (PIDs). Video packets pass through the uppermost path
(e.g., TB1 in FIG. 1), audio packets pass through a middle path (e.g.,
TBn in FIG. 1), and system control packets pass through the lowermost
path (e.g., TBsys in FIG. 1).

[0034] In the specification of the present invention, a description will
be given centering on the audio packets but the present invention may be
applied to the video packets or the system control packets. Accordingly,
the scope of the present invention should not be limited to the audio
packets of the embodiment, but defined by the accompanying claims and
equivalents thereof.

[0035] In FIG. 1, a TBn 110 denotes a transport buffer, a Bn 120 denotes a
main buffer, and a Dn 130 denotes a decoder.

[0036] The TBn 110 may have a size of 512 bytes. Data input to the TBn 110
is transmitted to the Bn 120 at a rate of RXn. The traveling rate to the
Bn 120 is 2 Mbps when the TBn 110 includes data and is 0 Mbps when the
TBn 110 does not include data. Overflow should not occur in the TBn 110.
However, when both mobile service data and main service data are
processed, an overflow problem in the TBn 110 is considered. A method for
solving this problem will be described in detail with reference to other
drawings.

[0037] The size of the Bn 120 may be 3,584 bytes or 2,592 bytes. A bit
stream, that is input at a rate of RXn, is transmitted to the Dn 130 at a
time tdn(j). In this case, tdn(j) is determined by a decoding time stamp
(DTS) transmitted through the bit stream. A system time clock (STC) is
recovered using a program clock reference (PCR). At a time point when the
recovered STC coincides with a DTS, data in the Bn 120 is transmitted to
the Dn 130. Overflow and underfloor should not occur in the Bn 120.
However, when both the mobile service data and the main service data are
processed, especially an overflow problem in the Bn 120 arises. A method
for solving this problem will be described in detail with reference to
other drawings.

[0038]FIG. 2 is a block diagram illustrating the construction of a
digital broadcast transmission system according to an exemplary
embodiment of the present invention. As illustrated in FIG. 2, a digital
broadcast transmission system 200 includes an MH frame controller 201, a
packet timing/PCR adjustment unit 202, a packet multiplexer (MUX) 210, an
MH frame encoder 205, a block processor 206, a signaling encoder 207, a
group formatter 208, a packet formatter 209, a modified data randomizer
212, a systematic/non-systematic RS encoder 213, a data interleaver 214,
a parity replacer 215, a non-systematic RS encoder 217, a modified
trellis encoder 216, a synchronization (Sync) MUX 218, a pilot inserter
219, a modulator 220, a radio frequency (RF) up-converter 221, and an
auxiliary buffer 203.

[0039] A module including the MH frame encoder 205, the block processor
206, the signaling encoder 207, the group formatter 208, and the packet
formatter 209 may be refereed to as a pre-processor 204.

[0040] A module including the modified data randomizer 212, the
systematic/non-systematic RS encoder 213, the data interleaver 214, the
parity replacer 215, the non-systematic RS encoder 217, and the modified
trellis encoder 216 may be referred to as a post-processor 211.

[0041] The packet MUX 210 multiplexes a main service data packet with a
mobile service data packet that is output from the packet formatter 209
in units of 188 bytes, according to a predefined multiplexing scheme and
outputs the multiplexed packet to the modified data randomizer 212. The
multiplexing scheme can be adjusted by various parameters of a system
design.

[0042] Meanwhile, the MH frame encoder 205 performs at least one of an
error correction encoding process and an error detection encoding process
when mobile service data is input thereto. Then robustness is provided to
the mobile service data and burst errors that may occur during changes in
a propagation environment are scattered, so that the mobile service data
can cope with the propagation environment that is extremely poor and
varies rapidly. The MH frame encoder 205 may include a process for mixing
mobile service data of a constant size in units of a row.

[0043] The error correction encoding process applies RS encoding and the
error detection encoding process applies cyclic redundancy check (CRC)
encoding, as an exemplary embodiment. When performing the RS encoding,
parity data to be used for error correction is generated, and when
performing the CRC encoding, CRC data to be used for error detection is
generated.

[0044] The RS encoding may use a forward error correction (FEC) structure.
FEC refer to a technique for correcting errors generated in a
transmission process. The CRC data generated by the CRC encoding may be
used to indicate whether the mobile service data is damaged by errors
while being transmitted through a channel. The present invention may use
error detection encoding methods other than the CRC encoding or may raise
overall error correction capabilities of a receiving side using the error
correction encoding method.

[0045] The mobile service data that is encoded by the MH frame encoder 205
is input to the block processor 206. The block processor 206 encodes the
input mobile service data at a code rate of G/H (where G<H) and
outputs the encoded data to the group formatter 208. Here, the signaling
encoder 207 may encode signaling data, independent of the MH frame
encoder 205, and may transmit the encoded signaling data to the group
formatter 208.

[0046] Namely, the block processor 206 divides the mobile service data
input in byte units into data of bit units, encodes G-bit data into H-bit
data, and converts the encoded data of bit units into data of byte units.
For example, if 1-bit input data is encoded into 2-bit data, then G=1 and
H=2, and if 1-bit input data is encoded into 4-bit data, then G=1 and
H=4. For convenience of description, the former case will be referred to
as encoding at a code rate of 1/2 (or 1/2-rate encoding) and the latter
case will be referred to as encoding at a code rate of 1/4 (or 1/4-rate
encoding).

[0047] Using 1/4-rate encoding accomplishes higher error correction
capabilities than using 1/2-rate encoding because of a higher code rate.
For such a reason, assuming that data encoded at a code rate of 1/4 in
the group formatter 208, which is located near an end part of the system,
is allocated to a region where reception performance may be degraded and
data encoded at a code rate of 1/2 is allocated to a region having better
performance, an effect of reducing the difference in performance can be
obtained.

[0048] The block processor 206 may receive from the signaling encoder 207
additional information data, such as signaling containing system
information etc. The 1/2 encoding or 1/4-rate encoding is performed upon
the additional information data in the same way as the mobile service
data processing process. Thereafter, the additional information data such
as signaling is regarded as the mobile service data and then is
processed. The signaling information is necessary to receive and process
data contained in a data group in a receiver and may include data group
information, multiplexing information, etc.

[0049] Meanwhile, the group formatter 208 inserts the mobile service data
generated from the block processor 206 into corresponding regions within
a data group formed according to a predefined rule, inserts various place
holders or known data related to data deinterleaving into corresponding
regions within the data group, and performs deinterleaving.

[0050] The data group may be divided into at least one hierarchical
region. The type of the mobile service data being inserted into each
region may vary according to the characteristics of each hierarchical
region. Each region may be divided based upon, for example, the reception
performance within the data group.

[0051] The reason why the data group is divided into a plurality of
regions is to use the regions according to different purposes. More
specifically, regions in which no interference or less interference from
the main service data may be considered to have a robust reception
performance as compared to regions having higher interference levels. In
a system that inserts known data into the data group and transmits the
data, when it is desired that consecutively long known data be
periodically inserted into the mobile service data, the known data having
a predetermined length may be periodically inserted in a region having no
interference from the main service data. However, in a region having
interference from the main service data, it is difficult to periodically
insert known data and to insert consecutively long known data into such a
region.

[0052] Further, the group formatter 208 inserts into the data group
additional information data, such as signaling, indicating overall
transmission information, independent of the mobile service data.

[0053] In addition to the encoded mobile service data generated from the
block processor 206, the group formatter 208 also inserts an MPEG header
place holder, a non-systematic RS parity place holder, and a main service
data place holder, which are related to data deinterleaving in a later
process. The main service data place holder is inserted because the
mobile service data and the main service data are alternately mixed with
each other in regions based upon data after the data deinterleaving
process is performed. For example, based upon the data output after data
deinterleaving, the MPEG header place holder may be allocated at the very
beginning of each packet.

[0054] The group formatter 208 inserts known data generated in accordance
with a predetermined method or inserts a known data place holder for
inserting the known data in a later process. Moreover, a place holder for
initializing the modified trellis encoder 216 is also inserted in a
corresponding region. For example, the initialization data place holder
may be inserted in the beginning of the known data sequence.

[0055] The size of the mobile service data that can be inserted into one
data group may vary according to the sizes of the trellis initialization
or known data, MPEG header, and RS parity place holders.

[0056] The output of the group formatter 208 is transmitted to the packet
formatter 209. The packet formatter 209 removes the main service data
place holder and the RS parity place holder that have been allocated for
the deinterleaving process from the deinterleaved input data. Then, the
packet formatter 209 collects the remaining portion and inserts an MPEG
header in a 4-byte MPEG header place holder.

[0057] When the group formatter 208 inserts the known data place holder,
the packet formatter 209 may insert actual known data in the known data
place holder, or may directly output the known data place holder without
modification in order to perform replacement insertion in a later
process.

[0058] Thereafter, the packet formatter 209 identifies data within the
packet-formatted data group as described above, as a mobile service data
packet (i.e., MPEG TS packet) of a 188-byte unit, which is then provided
to the packet MUX 210.

[0059] Meanwhile, if input data is a main service data packet, the
modified data randomizer 212 randomizes the input data in the same way as
a conventional randomizer. Namely, the modified data randomizer 212
discards a synchronization byte within the main service data packet and
randomizes the remaining 187 bytes using a pseudo random byte generated
therein. Thereafter, the modified data randomizer 212 outputs the
randomized data to the systematic/non-systematic RS encoder 213.

[0060] However, if the input data is a mobile service data packet, the
modified data randomizer 212 deletes a synchronization byte from the
4-byte MPEG header included in the mobile service data packet and
performs randomization only upon the other 3 bytes. The modified data
randomizer 212 does not perform randomizing upon the other mobile service
data except for the MPEG header and outputs the mobile service data to
the systematic/non-systematic RS encoder 213.

[0061] The systematic/non-systematic RS encoder 213 performs an RS
encoding process upon the data being randomized by the modified data
randomizer 212 or upon the data bypassing the modified data randomizer
212, so as to add a 20-byte RS parity. The processed data is output to
the data interleaver 214. If the input data corresponds to the main
service data packet, the systematic/non-systematic RS encoder 213
performs the same systematic RS encoding process as in a conventional
advanced television systems committee (ATSC) vestigial sideband (VSB)
system, thereby adding the 20-byte RS parity to the end of 187-byte data.
If the input data corresponds to the mobile service data packet, the
systematic/non-systematic RS encoder 213 performs a non-systematic RS
encoding process. At this point, the 20-byte RS parity obtained from the
non-systematic RS encoding process is inserted in a predetermined parity
byte location within the mobile service data packet.

[0062] The data interleaver 214 corresponds to a convolutional interleaver
of a byte unit.

[0063] The output of the data interleaver 214 is input to the parity
replacer 215 and to the non-systematic RS encoder 217.

[0064] Meanwhile, in order to decide the output data of the modified
trellis encoder 216, which is located after the parity replacer 215, as
the known data predefined according to an agreement between a
transmitting side and a receiving side, a process of initializing a
memory within the modified trellis encoder 216 is primarily required.
That is, the memory of the modified trellis encoder 216 should be
initialized before the input known data sequence is trellis-encoded.

[0065] In this case, the beginning portion of the input known data
sequence corresponds to the initialization data place holder inserted in
the group formatter 208, rather than the actual known data. Therefore, a
process of generating initialization data immediately before the input
known data sequence is trellis-encoded and replacing the initialization
data place holder of the corresponding memory with the generated
initialization data is required.

[0066] A value of the trellis memory initialization data is decided and
generated based upon a memory status of the modified trellis encoder 216.
Further, due to the newly replaced initialization data, a process of
newly calculating the RS parity and replacing the RS parity, which is
output from the data interleaver 214, with the newly calculated RS parity
is required.

[0067] Therefore, the non-systematic RS encoder 217 receives the mobile
service data packet including the initialization data place holder, which
is to be replaced with the actual initialization data, from the data
interleaver 214 and also receives the initialization data from the
modified trellis encoder 216.

[0068] The non-systematic RS encoder 217 replaces the initialization data
place holder within the input mobile service data packet with the
initialization data and eliminates the RS parity data that are added to
the mobile service data packet. Thereafter, the non-systematic RS encoder
217 calculates a new RS parity and outputs the RS parity to the parity
replacer 215. Accordingly, the parity replacer 215 selects the output of
the data interleaver 214 as data within the mobile service data packet
and selects the output of the non-systematic RS encoder 217 as the RS
parity. The selected data is then output to the modified trellis encoder
216.

[0069] Meanwhile, if the main service data packet is input, or if the
mobile service data packet, which does not include any initialization
data place holders that are to be replaced, is input, the parity replacer
215 selects the data and RS parity that are output from the data
interleaver 214. Then, the parity replacer 215 directly outputs the
selected data to the modified trellis encoder 216 without any
modification.

[0070] The modified trellis encoder 216 converts data of a byte unit into
data of a symbol unit and performs a 12-way interleaving process so as to
trellis-encode the received data. Thereafter, the modified trellis
encoder 216 outputs the processed data to the synchronization MUX 218.

[0071] The synchronization MUX 218 inserts a field synchronization signal
and a segment synchronization signal to the data output from the modified
trellis encoder 216 and, then, outputs the processed data to the pilot
inserter 219.

[0072] The pilot inserter 219 inserts a pilot to the data received from
the synchronization MUX 218 and the modulator 220 VSB-modulates the data
received from the pilot inserter 219. The modulated data is transmitted
to each broadcast receiving system or a digital broadcast receiver though
the RF up-converter 221.

[0073] To prevent an underfloor or overflow phenomenon of a buffer due to
a packet, the exemplary embodiment of the present invention may include,
as illustrated in FIG. 2, the packet timing/PCR adjustment unit 202, the
auxiliary buffer 203, and the MH frame controller 201.

[0074] It is assumed that the size of an MH frame is about 968
milliseconds (ms), and the MH frame may be divided into 5 subframes. Each
subframe is divided into 16 slots, each of which contains 156 consecutive
TS packets. Among the 156 TS packets, 118 TS packets are allocated as an
MH data region. The MH data region may mean a region in which the MH
service data is allocated. If much MH data is present, MH data can be
allocated to more slots. The MH data may correspond to the mobile service
data.

[0075] Meanwhile, if the mobile service data is transmitted by allocating
the MH data region as described above, a main service data packet cannot
be transmitted at that moment. Therefore, a transmission order of the
main service data packet that has not been transmitted should be changed
so that the main service data packet can be transmitted in a region
except for the region where the mobile service data is transmitted. The
packet timing/PCR adjustment unit 202 is designed to perform such a
function.

[0076] The packet timing/PCR adjustment unit 202 serves to correct changed
time information as the time location of the main service data packet
including a PCR is changed. To prevent buffer overflow, the packet
timing/PCR adjustment unit 202 changes the location of an audio packet.
Further, to prevent buffer underflow that occurs according to the
location change of the audio packet, the packet timing/PCR adjustment
unit 202 delays the reference time of the PCR.

[0077] To check whether underflow occurs in the buffers shown in FIG. 1,
the following assumption is made.

[0078] If the audio packet is sampled at 32 kHz and is encoded at 384
kbps, one frame becomes 48 ms and a data size corresponds to 13 TS
packets. Assuming that a DTS is set such that the audio packet is
transmitted as fast as possible and is decoded as soon as transmission is
completed, the size of data contained in the TBn 110 is shown in FIG. 3.

[0079] In FIG. 3, the horizontal axis corresponds to an index of a TS
packet and the vertical axis indicates the size of data contained in the
TBn 110. The period from when data is stacked in the TBn 110 to when the
TBn 110 is empty corresponds to the period when one audio frame is
shifted to Bn from TBn.

[0080] As shown in FIG. 3, if 9.91 ms elapses after the first audio TS
packet is input, the TBn 110 is empty again. After this time point, the
audio decoder such as the Dn 130 can decode the audio frame. That is, if
a DTS value of an audio packetized elementary stream (PES) packet header
contained in the first TS packet corresponds to an STC value after 9.91
ms elapses, underflow does not occur. Specifically, if a decoding process
is performed in a region `a` shown in FIG. 3, underflow does not occur.

[0081] A phenomenon appearing when a main service data encoded stream is
transmitted together with mobile service data will now be described. FIG.
4 shows the case where the mobile service data, that is, MH data is
maximally transmitted. As described previously, the 118 TS packets are
consecutively transmitted in the MH data. A main service data packet
should be transmitted between intervals or slots in which the MH data is
transmitted. Then the moment when TBn is empty becomes 34.05 ms, which is
further delayed by 24.14 ms as compared to when the MH data is no longer
present in FIG. 3.

[0082] Even though the MH data, etc. is transmitted, if a decoding process
that does not consider the mobile service data is performed at any time
point in the region `a` shown in FIG. 3, especially at an early time
point in the region `a`, without considering the MH data or mobile
service data, a probability of generating underflow is high. This is
because a data packet is shifted to the audio decoder from the audio
buffer under the state that the Bn 120 is not completely filled with
data.

[0083] Meanwhile, regions `b`, `c`, `d`, `e`, `f`, `g`, and `h` may
correspond to time zones when the main service data packet is not input.

[0084] The present invention is designed such that a PCR is adjusted in
order to prevent such an underflow phenomenon. Namely, by comparing FIG.
3 with FIG. 4, which are obtained experimentally, the reference time of
the PCR is delayed by more than 24.14 ms that is a time difference (34.05
ms-9.91 ms=24.14 ms) in FIG. 3 and FIG. 4. It is possible to sufficiently
fill the main buffers by delaying a time at which the decoder operates.
The time of 24.14 ms is a value obtained experimentally and the underflow
phenomenon may be eliminated to some degree even if a time of 24 to 25 ms
is applied.

[0085] According to another exemplary embodiment, not only the underflow
phenomenon of the buffers, for example, the TBn 110 and the Bn 120 but
also the overflow phenomenon thereof is substantially eliminated.

[0086] In the above description, the case where the audio packet is
transmitted as fast as possible and is decoded as soon as transmission is
completed has an underflow problem. Meanwhile, when the audio packet is
designed such that the audio packet is transmitted rapidly but as much
data as possible is stacked in the main buffer Bn 120, an overflow
problem occurs.

[0087] FIG. 5 shows a main buffer different from a transport buffer of
FIG. 3 and FIG. 4. In FIG. 5, the horizontal axis corresponds to an index
of a TS packet and the vertical axis indicates the size of data included
in the Bn. FIG. 5 shows the case where as much data as possible is
stacked in the main buffer and is then decoded. In this case, the mobile
service data (or MH data) is also transmitted together with the main
service data.

[0088] As shown in FIG. 5, if audio packet data is transmitted, the audio
packet data is stacked in the Bn 120. If the stacked audio packet data is
transmitted to the audio decoder 130 at a time point of DTS(i), only a
small amount of data remains in the Bn 120. If other frames are
consecutively input again, the audio packet data is stacked in the Bn 120
again after the time point of DTS(i). However, if the reference time of a
PCR is delayed to prevent underfloor of the TBn 110 as described above,
then a large amount of data is stacked in the Bn 120 as illustrated in
FIG. 6. Namely, since the reference time of the PCR is delayed, actual
decoding time is also delayed and a large amount of data is unexpectedly
stacked in the Bn 120, thereby resulting in an overflow phenomenon of the
Bn 120.

[0089] To remove the overflow phenomenon of the Bn 120, the MH frame
controller 201, the packet timing/PCR adjustment unit 202, and the
auxiliary buffer 203 are newly defined as illustrated in FIG. 2 according
to the exemplary embodiment of the present invention.

[0090] If the digital broadcast transmission system 200 processes
broadcasting signals including the main service data and the mobile
service data, the packet timing/PCR adjustment unit 202 delays the
reference time of the PCR based on the size of the mobile service data.

[0091] More specifically, the packet timing/PCR adjustment unit 202 delays
the reference time of the PCR by a time of 24 to 25 ms, as a result of
comparing the case where the broadcasting signals including the main
service data are processed with the case where broadcasting signals
including both the main service data and the mobile service data are
processed. Therefore, when a TS packet satisfying a T-STD model 100 of
FIG. 1 is transmitted through a process for enabling the packet
timing/PCR adjustment unit 202 to delay the reference time of the PCR,
the underfloor phenomenon of the transport buffer 110 can be prevented.
The T-STD model 100 of FIG. 1 may correspond to an MPEG2 T-STD.

[0092] The packet timing/PCR adjustment unit 202 or an additional module
verifies the T-STD model 100 of FIG. 1, based on the PCR of the delayed
reference time, before the broadcasting signals are transmitted. Further,
the packet timing/PCR adjustment unit 202 determines whether overflow of
the main buffer 120 of the T-STD model 100 is estimated, as a result of
verifying the T-STD model 100.

[0093] The packet timing/PCR adjustment unit 202 or the additional model
prevents the T-STD model 100 from overflowing in the main buffer 120,
using the determination result. Such an operation is a process for
preventing an overflow phenomenon which may appear in the Bn 120 shown in
FIG. 1 as the reference time of the PCR is delayed.

[0094] The control process of the packet timing/PCR adjustment unit 202 or
the additional module will now be described in detail.

[0095] If the overflow is estimated as the determination result, the
packet timing/PCR adjustment unit 202 or the additional module stores a
packet received in the main buffer 120 in the auxiliary buffer 203. The
packet timing/PCR adjustment unit 202 or the additional module replaces
the received packet with a null packet and performs a control function to
transmit a broadcasting signal including the null packet.

[0096] The packet timing/PCR adjustment unit 202 or the additional module
performs a control operation to store a replacing order in the above
replacing process, and corrects an order of a packet to be transmitted to
an original order using the stored replacing order, during transmission
of the broadcasting signal.

[0097] If the overflow is not estimated as the determination result, the
packet timing/PCR adjustment unit 202 or the additional module identifies
whether the packet received in the main buffer 120 is a null packet. If
the received packet is the null packet, the packet timing/PCR adjustment
unit 202 or the additional module replaces the null packet with the
packet which has been previously stored in the auxiliary buffer 203 and
returns to the verification process.

[0098] FIG. 7 is a flow chart illustrating a data processing method of a
digital broadcast transmission system according to an exemplary
embodiment of the present invention.

[0099] The digital broadcast transmission system determines whether a
packet corresponds to a PCR packet including PCR information in step
S700. If the packet corresponds to a PCR packet in step S700, the digital
broadcast transmission system delays the reference signal of a PCR in
step S701. The delay time may be determined in proportion to the size of
mobile service data and may be a time delay in the range of 24 to 25 ms.
More specifically, the time delay may be 24.14 ms.

[0100] The digital broadcast transmission system verifies the T-STD model
based on the PCR of the delayed reference time in step S702, before
transmitting a broadcasting signal. The digital broadcast transmission
system determines whether a main buffer of the T-STD model is in a full
state in step S703, as a result of verifying the T-STD model in step
S702.

[0101] The full state may mean that the main buffer is completely full or
is almost full.

[0102] The digital broadcast transmission system prevents the T-STD model
from overflowing the main buffer using the determination result. Such a
control process may be implemented using the whole steps or partial steps
of steps S704 to S711 shown in FIG. 7.

[0103] If the main buffer is full in step S703, the digital broadcast
transmission system stores the packet received in the main buffer in the
auxiliary buffer of the main buffer in step S704 and replaces the
received packet with a null packet in step S705.

[0104] The digital broadcast transmission system determines whether a new
packet corresponds to a PCR packet including PCR information in step
S706. If the new packet does not correspond to a PCR packet, the digital
broadcast transmission system transmits a broadcasting signal including
the replaced null packet in step S708. However, if the new packet
corresponds to the PCR packet in step S706, the digital broadcast
transmission system restamps the PCR according to the changed order of
the packet in step S707.

[0105] Another exemplary embodiment for implementing steps S707 and S708
may include a step of storing the packet replacing order in steps S704
and S705, and a step of correcting an order of a packet to be transmitted
to an original order using the stored packet replacing order.

[0106] Meanwhile, if the main buffer of the T-STD model is not in a full
state in step S703, the digital broadcast transmission system identifies
whether the packet received in the main buffer is a null packet in step
S709. If the received packet is a null packet, the digital broadcast
transmission system determines whether another packet has been stored in
the auxiliary buffer in step S710.

[0107] If another packet has been stored in step S710, the digital
broadcast transmission system replaces the null packet with the packet
stored in the auxiliary buffer in step S711 and returns to step S702.

[0108] FIG. 8 is a block diagram illustrating a digital broadcast receiver
according to an exemplary embodiment of the present invention. The
digital broadcast receiver of FIG. 8 can improve reception performance by
performing carrier synchronization recovery, frame synchronization
recovery, channel equalization, etc. using known data information, that
is inserted into a mobile service data interval in a transmission system
and then is transmitted.

[0109] A digital broadcast receiver 800 of the present invention includes
a tuner 801, a demodulator 802, an equalizer 803, a known sequence
detector 804, a block decoder 805, an RS frame decoder 807, a
derandomizer 808, a data deinterleaver 809, an RS decoder 810, and a data
derandomizer 811. For convenience of description, the RS frame decoder
807 and the derandomizer 808 will be referred to as a mobile service data
processor, and the data deinterleaver 809, the RS decoder 810, and the
data derandomizer 811 will be referred to as a main service data
processor.

[0110] The tuner 801 tunes to a frequency of a specific channel and
down-converts the tuned frequency to an intermediate frequency (IF)
signal. Then, the tuner 801 outputs the down-converted IF signal to the
demodulator 802 and to the known sequence detector 804.

[0111] The demodulator 802 performs automatic gain control, carrier
recovery, and timing recovery processes upon the input IF signal, thereby
converting the IF signal into a baseband signal. Thereafter, the
demodulator 802 outputs the baseband signal to the equalizer 803 and to
the known sequence detector 804.

[0112] The equalizer 803 compensates for the distortion of a channel
included in the demodulated signal and then outputs the
distortion-compensated signal to the block decoder 805.

[0113] The known sequence detector 804 detects a known data place inserted
by the transmitting system from the input/output data of the demodulator
802, that is, the data before or after the demodulation process.
Thereafter, the know sequence detector 804 outputs, along with the place
information, a symbol sequence of the known data, which is generated from
the detected place, to the demodulator 802 and to the equalizer 803. The
known sequence detector 804 further outputs to the block decoder 805
information that is used to allow the block decoder 805 to identify
mobile service data upon which additional encoding is performed in the
transmission system and main service data upon which additional encoding
is not performed. Although a connection status is not shown in FIG. 8,
the information detected from the known sequence detector 804 may be used
throughout the entire receiver and may also be used in the RS frame
decoder 807.

[0114] The demodulator 802 uses the known data symbol sequence during the
timing recovery or carrier recovery, thereby enhancing demodulation
performance. Similarly, the equalizer 803 uses the known data so as to
enhance the equalizing performance. Moreover, the decoding result of the
block decoder 805 may be fed back to the equalizer 803, thereby enhancing
the equalizing performance.

[0115] Meanwhile, if the data input to the block decoder 805 after being
channel equalized from the equalizer 803 corresponds to data (e.g., data
within an RS frame) upon which both block encoding and trellis encoding
processes have been performed by the transmitting system, trellis
decoding and block decoding processes are performed on the input data as
inverse processes of the transmission system. Alternatively, if the data
input to the block decoder 805 corresponds to data (e.g., main service
data) upon which only the trellis encoding has been performed without
block encoding, only the trellis decoding process is performed on the
input data.

[0116] The data trellis-decoded and block-decoded by the block decoder 805
is input to the RS frame decoder 807. Namely, the block decoder 805
eliminates known data, data used for trellis initialization, signaling
information data, and an MPEG header, which are inserted in a data group,
and RS parity data, which is added by the systematic/non-systematic RS
encoder or the non-systematic RS encoder of the transmission system.
Thereafter, the block decoder 805 outputs the processed data to the RS
frame decoder 807. The removal of the data may be performed before the
block decoding process, or may be performed during or after the block
decoding process.

[0117] Meanwhile, the data trellis-decoded by the block decoder 805 is
output to the main service data processor. The data that is
trellis-decoded by the block decoder 805 and output to the main data
processor may include data and signaling information within the RS frame
as well as the main service data. Moreover, the RS parity data that is
added after the pre-processor of the transmission system may be included
in the data that is output to the main service data processor.

[0118] As another exemplary embodiment, the data upon which only the
trellis encoding has been performed and the block encoding has not been
performed by the transmission system may bypass the block decoder 805 so
as to be directly input to the main service data processor. In this case,
a trellis decoder should be provided before the main service data
processor. The main service data processor may be designed to be located
at a position where a signal can be received from the block decoder 805
of FIG. 8.

[0119] If the input data corresponds to data upon which only the trellis
encoding has been performed and the block encoding has not been performed
in the transmission system, the block decoder 805 may perform Viterbi
decoding on the input data so as to output a hard decision value or to
perform a hard-decision on a soft decision value, and may output the
result.

[0120] Meanwhile, if the input data corresponds to data upon which both
the block encoding and the trellis encoding have been performed in the
transmission system, the block decoder 805 outputs a soft decision value
with respect to the input data.

[0121] More specifically, if the input data corresponds to data upon which
the block encoding has been performed by the block processor of the
transmission system and the trellis encoding has been performed by the
trellis encoder of the transmission system, the block decoder 805
performs trellis decoding and the block decoding which are inverse
processes of the transmission system. In this case, the block processor
of the transmission system may be an external encoder and the trellis
encoder may be an internal encoder.

[0122] To maximize the performance of an external code when decoding
concatenated codes, the decoder of an internal code should output a soft
decision value.

[0123] Therefore, the block decoder 805 may output a hard decision value
on the mobile service data. However, when required, it may be more
desirable for the block decoder 805 to output a soft decision value.

[0124] Meanwhile, the data deinterleaver 809, the RS decoder 810, and the
derandomizer 811 are blocks required for receiving the main service data.
Therefore, the above-mentioned blocks may not be required in the
structure of a receiving system for receiving only the mobile service
data.

[0125] The data deinterleaver 809 performs an inverse process of the data
interleaver of the transmission system. In other words, the data
deinterleaver 809 deinterleaves the main service data output from the
block decoder 805 and outputs the deinterleaved main service data to the
RS decoder 810.

[0126] The RS decoder 810 performs a systematic RS decoding process upon
the deinterleaved data and outputs the processed data to the derandomizer
811.

[0127] The derandomizer 811 receives the output of the RS decoder 810 and
generates a pseudo random data byte identical to that of the randomizer
of the transmission system. Thereafter, the derandomizer 811 performs a
bitwise exclusive OR (XOR) operation upon the generated pseudo random
data byte, thereby inserting an MPEG synchronization byte into the
beginning of each packet so as to output data in 188-byte main service
data packet units.

[0129] The RS frame decoder 807 performs an inverse process of the RS
frame encoder of the transmission system so as to correct errors within
the RS frame. Then, the RS frame decoder 807 adds the 1-byte MPEG
synchronization service data packet, which has been removed during the RS
frame encoding process, into the error-corrected mobile service data
packet. Thereafter, the RS frame decoder 807 outputs the processed data
to the derandomizer 808.

[0130] The derandomizer 808 performs a derandomizing process corresponding
to the inverse process of the randomizing process of the transmission
system upon the received mobile service data. Therefore, the mobile
service data transmitted from the transmission system can be obtained.

[0131] According to the exemplary embodiment of the present invention, the
digital broadcast receiver can process the broadcasting signal including
packets which do not generate underfloor or overflow.

[0132] The tuner 801 receives a broadcasting signal including a main
service data packet, a mobile service data packet, and a PCR of which
reference time is delayed. A module in charge of the function of the
tuner 801 may be referred to as a receiver.

[0133] According to the exemplary embodiment of the present invention, the
tuner 801 receives a broadcasting signal including a null data packet
instead of the main service data packet from the digital broadcast
transmission system, according to the verification process result of the
T-STD model.

[0134] The block decoder 805 demultiplexes the received broadcasting
signal. A module in charge of the function of the block decoder 805 may
be referred to as a demultiplexer.

[0135] The data interleaver 809, the RS decoder 810, and the data
derandomizer 811 decode the demultiplexed main service data packet using
the demultiplexing result, that is, according to the PCR. A module in
charge of such a function may be referred to as a decoder.

[0136] Therefore, according to the exemplary embodiment of the present
invention, adding the mobile service data to the existing main service
data can solve all estimated underflow and overflow problems. For
example, first, the underflow phenomenon in the buffer of the T-STD model
can be substantially removed by delaying the reference time of the PCR to
a prescribed range. Second, the overflow phenomenon in the main buffer of
the T-STD model can be substantially removed by adding the auxiliary
buffer and through a verification process for the T-STD model.

[0137] According to the exemplary embodiment of the present invention, the
overflow and underflow problems of the T-STD model can be prevented by
adding the MH data to the TS stream satisfying the T-STD.

[0138] According to the exemplary embodiment of the present invention,
since the digital broadcast transmission system pre-checks the underflow
and overflow, the underflow and overflow problems do not occur in the
buffer of the digital broadcast receiver.

[0139] Meanwhile, in this specification, an article invention and a method
invention have been described, and the article invention and the method
invention include similar technical spirits. A description of the article
invention may be applied to the method invention, and conversely, the
method invention may be applied to the article invention.

[0140] The invention of the method according to the present invention may
be implemented in the form of program commands that are capable of being
performed through various computer means and then may be recorded in
computer readable media. The computer readable media may include program
commands, data files, data structures, etc. in an independent or combined
form. Program commands recorded in the media may be designed and
constructed particularly for the present invention or may be known to
those skilled in the art. The computer readable media includes hardware
devices that are configured to store and perform program commands. For
example, the computer readable media includes magnetic media (e.g., hard
discs, floppy discs, and magnetic tapes), optical media (e.g., CD-ROMs
and DVDs), magneto-optical media (e.g., floptical disks), a ROM, a RAM, a
flash memory, etc. The program commands include advanced language codes,
that can be implemented by a computer using an interpreter, etc., as well
as machine languages, that are configured by a compiler. The
aforementioned hardware devices may be constructed to be operated as one
or more software modules for carrying out the operation of the present
invention, and an inverse process may be applied.

[0141] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention without
departing from the spirit or scope of the inventions.

[0142] Thus, it is intended that the present invention covers the
modifications and variations of this invention provided they come within
the scope of the appended claims and their equivalents.